It is known in the prior art to inspect an object by illuminating it with penetrating radiation. Some of the radiation may pass through the object, and some may be absorbed or deflected by the object. Some of the illuminating radiation, however, will be scattered in all directions, such as back in the general direction from which it came, in which case the scattered radiation may be referred to as backscatter radiation. Such scattered radiation may pass into a detector (which may be referred to, herein, as a “scatter detector,” and some portion of that scattered radiation will be detected by the detector.
Existing systems for inspection of objects, for security applications, for example, employ scatter detectors that are fixed in position relative to the beam of illuminating radiation, or that, upon reorientation, subtend substantially the same solid angle with respect to the inspected object as before reorientation. One such system with reconfigurable scatter detectors is shown in FIGS. 5A and 5B of U.S. Pat. No. 5,764,683. Such inspection systems, however, are designed for inspection, at specified range, on the order of a meter, of a particular class of objects (namely, cars and trucks), which are inspected at a substantially fixed distance with respect to the inspection system. Such inspection systems cannot provide for substantial variation in the footprint of the detector array when called upon for inspection in particularly close quarters, or so as to accommodate substantial variation in the distance between the inspection system and the inspected object. The latter might be necessary in a field deployment, where the inspected object may be disposed at a substantial distance from the inspection system.